1. Field of the Invention
The present invention relates to a sensor unit and a control system including the sensor unit. Particularly, the sensor unit unitarily has a sensor fitted to an automobile vehicle for producing a load signal responsive to a load carried by the vehicle and an adjustment means adjusting the load signal supplied from the sensor to output externally the adjusted load signal.
2. Related Art
A vehicle dead weight measurement has been applied mainly to a larger-sized vehicle such as a truck to prevent turn over of the vehicle due to an over-load condition thereof at a traffic accident or to decease degradation of the vehicle due to the over load. A conventional dead weight measurement of the vehicle, in which the vehicle is carried on a platform weighing machine, requires a large scale facility with a wide space. This limits the number of the platform weighing machines to be unsuitable for weight-measurement of a large number of the vehicles. Furthermore, the platform weighing machine requires a larger installation cost thereof.
Recently, a weight meter mounted on a vehicle has been proposed to measure the dead weight thereof. The weight indicator has, for example, a plurality of weight measuring sensors such as a strain gauge. The weight measuring sensors are mounted at fore, aft, left, and right positions of a carrier frame of the vehicle to sum outputs responsive to sensed loads, obtaining a dead weight of the vehicle. Each of the sensors is mounted on an arc-shaped leaf spring disposed between a vehicle axle and an end of the carrier frame.
The sensors are positioned at pre-determined positions near the axles and are connected to a weight meter through electrical cables. An amplifier is disposed in a cable line led to the weight meter for amplifying a load signal output from each of the sensors. The amplifier amplifies the load signals to eliminate an influence of noises generated by vibrations of the vehicle.
However, the conventional weight meter has a disadvantage that plural types of amplifiers should be provided for different types of vehicles, when the weight meter is connected to a sensor through an amplifier, because the amplifier should have an amplification ratio fit for each type of the vehicles.
The sensor is welded to an axle support or a shackle pin of the vehicle. The welding may vary the output of the sensor. Thus, the amplifier has an adjustment element such as a volume in a circuit thereof. After the welding of the sensor, a worker removes a waterproof case cover of the sensor to adjust the volume of the sensor with a screwdriver for an offset adjustment of the sensor.
Therefore, the amplifier should be arranged at a position where the worker can easily handle it, so that the amplifier is not disposed near the sensor welded to the vehicle axle support. However, it is preferable that the load signal of the sensor is amplified or adjusted near the sensor in consideration of an influence of a noise. Thus, an adjustment means like an amplifier which can be disposed near the sensor has been desired. However, a conventional adjustment component as an adjustment means is adjusted with a screwdriver by hand. Thus, it is difficult to correctly adjust the amplifier, which causes a troublesome work, since the adjustment component becomes misaligned when the screw driver releases the adjustment component.
In view of the above-mentioned disadvantage of the conventional art, an object of the present invention is to provide a sensor unit having an adjustment means and a sensor which are unitarily assembled and or to provide a sensor unit control system for adjusting the sensor unit.
Referring to a block diagram illustrated in FIG. 1, the present invention will be discussed.
For achieving the object, a first aspect of the present invention is a sensor unit having a unit main body unitarily including a sensor 11 fitted to an automobile vehicle for producing a load signal responsive to a load carried by the vehicle and an adjustment means 12 adjusting the load signal supplied from the sensor 11 to output externally the adjusted load signal. The sensor unit further has a receiver means 15 positioned outside of the unit main body for receiving modification information for modifying the adjustment of the load signal, and the adjustment means 12 adjusts the load signal to output the load signal after the receiver means 15 receives the modification information.
The sensor unit having the sensor 11 and the adjustment means 12 is welded on the vehicle. After the mounting of the sensor unit, the receiver mean receives externally the modification information for modifying the load signal adjustment. Thereby, the load signal outputted from the sensor 11 is adjusted by the adjustment means 12 responsive to the modification information to be externally outputted. Thus, after the mounting of the sensor unit, the receiver mean receives the modification information, and the adjustment means 12 adjusts the load signal supplied from the sensor 11 based on the modification information. This allows the sensor unit to unitarily have the sensor 11 and the adjustment means 12. Thereby, the adjustment means 12 can be modified by the modification information externally supplied. Hence, the sensor unit with the adjustment means 12 can be applied to various types of vehicles. This eliminates the offset adjustment required after the mounting of the prior-art sensor, decreasing handwork of the adjustment.
Preferably, the receiver means 15 serves as a coupler for connection to an external instrument.
Thus, the connection of the receiver mean to the external instrument allows the sensor unit to connect to the external instrument with ease. That is, the receiver mean can be located at a position where it is easily connected to the external instrument, even when the sensor unit is mounted near the vehicle axle. This further decreases handwork of the adjustment.
Preferably, the receiver means 15 receives externally an output timing signal of the load signal, and the adjustment means 12 outputs the load signal in response to the output timing signal received by the receiver means 15.
Thus, the load signal can be outputted responsive to the received output timing signal, so that the load signal supplied from the sensor 11 is outputted responsive to an operation of the external instrument. This allows the sensor unit to easily co-operate an external instrument such as a vehicle instrument unit or a vehicle control unit, improving the sensor unit as a commercial product.
A sensor unit control system according to the present invention has the sensor unit described in the first invention aspect. The control system includes a modification information producing means 30a1 for producing the modification information responsive to a state of the vehicle and a transmission means 30a2 for transmitting the modification information produced by the modification information producing means 30a1 to the receiver means 15 of the sensor unit.
In the sensor unit control system, the modification information producing mean produces the modification information for adjustment responsive to a gain and a temperature of the vehicle. The modification information is supplied to the receiver mean 15 of the sensor unit by the transmission means 30a2. The sensor unit externally outputs the load signal adjusted responsive to the received modification information. Thus, the modification information which is produced particularly for a vehicle provided with the sensor unit is transmitted to the sensor unit, so that the sensor unit outputs the load signal adjusted responsive to the modification information. Thereby, the sensor unit having the sensor 11 and the adjustment means 12 can be easily adjusted. Hence, the modification information can adjust the sensor unit responsive to the type of the vehicle. Accordingly, the control system having the sensor unit can be applied to various different types of vehicles.
Preferably, the sensor unit control system further includes a load data receiver means 30g1 for receiving load data which are outputted from the sensor unit, the load data being related to the load signal. The modification information producing means 30a1 produces the modification information based on pre-provided vehicle weight data and the load data received by the load data receiver means 30g1.
Thus, the modification information can be produced based on the load data supplied from the sensor unit and the pre-provided vehicle weight data showing a reference load of the vehicle. Accordingly, even if the output of the sensor 11 would vary due to the welding of the sensor 11, the adjustment means 12 can be adjusted based on the load signal supplied from the sensor unit. This allows a correct adjustment of the adjustment means of the sensor unit.
Preferably, the sensor unit control system further includes a vehicle weight measuring means 40 for measuring a vehicle weight of the vehicle to output vehicle weight data, and the control system also has a vehicle weight receiver means 30g2 for receiving the vehicle weight data from the vehicle weight measuring means 40. The modification information producing means 30a1 provides the vehicle load data based on the vehicle weight data received by the vehicle weight receiver means 30g2.
Thus, the modification information is produced based on the vehicle weight data and the load data supplied from the sensor unit, and the vehicle weight data are actually measured by the vehicle weight measuring means 40. This allows a more correct adjustment of the control mean of the sensor unit.